Numerous problems exist in the field of blow-molding installations for packaging containers, such as bottles, made of synthetic material. First of all, in order to effect the blow-molding of the containers into a mold, a gas, such as air, must be available under a high pressure of the order of 40 bar. In order to compress the required gas, compressors are conventionally used. However, according to some blow-molding methods, a pre-molding of a preform, which will be transformed into a container, is firstly carried out, followed by the blow-molding process per se. The pre-molding is performed under a pressure of around 10 bar, then the blow-molding process reaches a pressure of 40 bar. A first way to obtain these two working pressures is to use two compressors, one to generate the pressure of 10 bar and the other to generate the pressure of 40 bar. However, the use of two compressors is costly both in terms of initial investment for their purchase and in terms of maintenance.
Another way of proceeding is to only use one compressor that compresses the gas to 40 bar, then to regulate a part of the compressed gas to 10 bar for the pre-molding operation. This method is not very advantageous either since energy is wasted in compressing a gas whose pressure is reduced without having used it in the manufacturing process.
Moreover, once the container has been formed by blow-molding, the compressed gas used (which is at a pressure of around 40 bar) is released into the open air which represents a waste of energy.
Thus, it has proved to be necessary to improve the known methods and machines in order to enhance their efficiency and to reduce this energy wastage.